These look like they are done in America and the seat belts look quite poorly designed compared to some in the uk.
The uk ones I've seen are made of seatbelt material and design, unlike the videos on the clips from what I can see on them.
It is definitely better than nothing at all and possibly the only option for large dogs. I wouldn't like a crate getting loose and flying in an accident so is also my option for small dogs if you have no crate for the boot area. It can and has saved dogs and people's lives.